1. Field of the Invention
The present invention relates generally to computer generated documents and in particular to computer generated index documents.
2. Description of Related Art
For many documents created on a computer, like text documents, HTML documents, presentations and others, related index pages are useful in finding desired content within the document, or are useful in getting information about bibliographic sources or the like. Index documents include documents that in turn include any or all of a table of contents, a headword index, figure or table index as well as a bibliographic index, for example, which are referred to herein as an index page.
Creating an index page involves a lot of formatting work, and is therefore time consuming and costly. An index page typically has a plurality of index lines having a specific content and format. In an index page that is a table of contents of a book, for example, there exist index lines for different hierarchical levels of headings, i.e., main heading, sub-heading etc.
FIG. 1 shows an example of an index page 100 that is a table of contents of a textbook. Index page 100 has a plurality of index lines, which have different functions and are formatted differently.
The first index line is the title “Contents” followed by the index line “Summary” with page number 5. Next are three index lines representing hierarchies of headings. A table of contents like that shown in FIG. 1 is an example of an index page, where the index lines represent a different level in a hierarchical order within the index page.
Another example is a bibliographic index, which can contain a plurality of different types of information sources like books, journals, theses, e-mails, www-pages and so on. Different types of index lines, in this example, do not represent different hierarchical levels, but do represent different types of information sources.
It is known to define the content and format of an index line using a string of instruction symbols (tokens) and attributes associated with the tokens. In the following an example of a token string with corresponding attributes (in parenthesis) is provided for an index line of a table of contents, such as that in FIG. 1:                chapter number CH (character style); entry text ET (style template); tabulator TAB (type, filling character, position); page number PN (character style).        
Typically, “chapter number” is represented by a numerical value, e.g., 1, 1.1, 1.3.5. “Entry text” is the chapter title and has a style defined by the style template. The tabulator filling character, e.g., a blank character or a dot, fills the space from the entry text to the page number. The tabulator has two other attributes, i.e., the tabulator type (centered, left, right) and a position measured in mm, inches or any other suitable metric. In most cases, the page number is positioned at the right side of the index line.
It is known to either input the token string directly by typing the instruction symbols and attribute values, or by using a user interactive menu dialog. These two methods are complicated and time consuming for the user. Furthermore, the problem arises that the syntax of tokens and attributes may be input incorrectly.
Arranging the tokens to define an order is particularly difficult to handle because tokens could be entered inside another token. Therefore, the computer program has to check the syntax of the input token string every time, and if the syntax is wrong, the token string has to be corrected by the user. Besides index pages other instruction sets, for example defining a modem interface, may have to be input into a computer with correct syntax.